Receiving circuit for wireless signaling



Feb. 19, 1929.. I I 1,702,440

. N. P. HINTON RECEIVING CIRCUIT FOR WIRELESS SIGNALING Filed June 1924 INVENTOR W I BY Wu @W/ ATTORNEY Patented Feb. 19, 1929.

UNITED STATES PATENT OFFICE.

NORMAN PULLEN HINTON, OF ALBERVILLE, ENGLAND, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO METROPOLITAN -VICKERS ELECTRICAL COMPANY, LIMITED, A BRITISH JOINT-STOCK COMPANY.

RECEIVING CIRCUIT FOR WIRELESS SIGNALING.

Application filed 1111102, 1924, Serial No. 717,235, and in Great Britain June 27, 1923.

My invention relates 'to receiving circuits for wireless telegraphy and particularly to receiving circuits having means for selective reception.

One object of my invention is to produce a radio receiving system having means for substantially reducing interference.

Another object of my invention is to pro duce a radio receiving system having means for substantially reducing static influences.

Another object of my invention is to produce a combination of an open aerial and a loop aerial.

Another object of my invention is to construct a combination of an aperiodic open aerial combined with a loop antenna Whereby signals received by one receptor are caused to neutralize undesired signals in the other receptor.

In the prior art of the construction of radio receiving apparatus, it has been common to use both open aerials and loop antennae, and attempts have been made to use them in combination, but all such structures have oper-' ated under the handicap that forced oscillations or untuned impulses, have produced serious interference with signals which it was desired to receive.

My invention provides a combination of an open aerial and a loop antenna whereby signals received by the one are caused to neutralize all of the undesired signals received by the other but only a portion of the desired signal.

According to my invention, signals are received upon an open aperiodic aerial and also upon a tunable loop aerial, and the respective electromotive forces, due to an undesired signal, are balanced out in the'frame aerial circuit. The vector diiference of the respective electromotive forces due to the different signals of different direction or Wave length or both is utilized for the compensation.

In carrying out my invention by a convenient arrangement, an aperiodic open aerial and a tunable loop aerial are combined with a three-electrode valve to form a reception circuit. The frame aerial forms part of the tuned anode circuit of the valve. The signal voltages in the open aerial are impressed on the grid of the valve the amplification factor of which can be adjusted to equalize the electromotive forces of an undesired signal in the respective antennae. The received signalsare rectified and amplified by the usual circuit arrangement whlch recelvmg circuit of can be coupled with the my invention.

In order to maintain symmetry in the loop aerial the high tension battery, which is con nected to the filamen at its negative end,

aerial at the electr t of the valve and earthed is connected to the loop ically symmetrical mid tion.

Referring to the drawing, an open aerial 1 1s in series with a high resistance 2, by means of which it is made effectively aperiodic in so far as concerns wave lengths of the order it is desired to receive.

The signal voltages across this high resistance'2 areimpressed on the grid 3 of the valve 4. The loop aerial is shown at 5 with a corresponding tuning condenser 6 across the terminals thereof. A

two-Way switch 7 is provided for connecting either of these terminals to the anode 8 of the valve 4. The high tension battery 9 is connected to the electrically symmetrical midpoint 10 of the loop aerial 5.

In order to secure accurate balance of the undesired lmpressed signal voltages it is necessary as set forth above to alter the mag nification factor of the valve.

sistance 2 on the hi gh resistance potentiometer 14 which shunts the filament battery 15. riation of the high aerial circuit.

The adjustment may also be made by varesistance 2 in the open The tuning condenser 6 is connected to the loop aerial by means of symmetrically placed inductances 16 and from either of these a variable coupling 17 may be arranged leading to the detector and the amplification circuits (not shown).

In order to recei Ve a desired signal and This may be eliminate an undesired interfering signal, the loop aerial is tuned to the undesired signal. Such tuning may be initially effected with the switch 7 in its open position so that the open aerial is cut out of circuit. Preliminary tuning of the loop aerial having been obtained the switch 7 is closed on either of its contacts and the amplification factor of the valve is adjusted by any of the means described until the electromotive forces impressed indirectly in the loop aerial from the open aerial through the valve and the electromotive forces in'ipressed directly in the loop aerial are equal.

N ow it is obvious that these electromotive forces will assist or oppose one another according to which of the two contacts the switch 7 engages. Such assistance or opposition of the respective electromotive forces may obviously also be obtained by rotating the loop aerial through an angle of 180. To eliminate. the undesired signal, the respective electromotive forces are caused to be exactly balanced out in the loop aerial circuit by final adjustment of the constants of the system. The desired signal which is of dif ferent wave length or is arriving from adifferent direction will now be received since the respective electromotive forces due thereto will not be balanced out.

This will clearly be the case since, if the desired signals are of different wave length the loop aerial is not tuned thereto and the indirect electromotive forces from the open aerial will, therefore, be different from the electromotive forces directly impressed in the loop aerial. If, on the other hand, the desired signals arrive from a different direc-. tion the orientation of the loop aerial will be different with a corresponding difference in the electromotive forces directly impressed thereon. Such directly impressed electromotive forceswill assist or oppose the electromotive forces derived from the open aerial according to whether the station transmitting the desired signals isangulmrly spaced more or less than 90 from the station transmitting the undesired signals.

The vectorial difference of the respective electromotive forces is in fact available. Strongest signals will be obtained when the two transmitting, stations are: in line with the receiving station and on opposite sides thereof. However, the desired signals can still be eflectively received .to the exclusion of the undesired signal even if the two stations are in line with the receiving station. and on the same side thereof, if the wave lengths of the two signals are different. The difference need only be small. It will be appreciated that the directional effects of the improved receiving circuit are absolute, be ing obtainable in accordance with the well known heart-shaped polar diagram.

Thus by the means described, the usual unidirectional reception can be obtained or interfering waves can be nullified. On moving the switch to its other operative position, or by rotating the loop throughlSO", maximum strength of signalswill be obtained, that is to say, the signals received by the open aerial will be strengthened by the addition of the voltageof those received by the loop aerial so that maximum signals will be to its open position as above mentioned. By

using a large open type aerial and by increasing the magnification factor of the valve, the arrangement can be made such".

that the effect of the loop aerial will be negligible for the desired signal and the ordinary open aerial reception obtained with the loop aerial forming part of the tuned anode circuit.

The open type aerial may in some instances be embodied in the loop aerial by using, a split metallic former or frame forthe conductors of the loop aerial, for example, or by conductors supported by the frame which would act as an open type aerial, or other methods may be used for utilizing the open type aerial effect of the loop aerial itself.

While I have shown only one embodiment of my invention, it is capable of various changes and modifications therefrom without departing from the spirit thereof and it is: desired, therefore, that only such'limitations shall be imposed thereon as are indicated in the pror art or in the appended claims.

I claim as my invention:

1. A selective receiving circuit for wireless telegraphy and telephony comprising an aperiodic open aerial, a tunable loop aerial and means for equalizing the electromotive forces derived from the open aerial due to a given signal with the corresponding electromotive force in the loop-aerialcircuit'and for applying said equalized open-aerial electromotive forces to the loop-aerial circuit to oppose and balance out the aforesaid loopaerial electromotive forces, whereby the respective electromotive forces due to another signal of different direction or wave length or both are not balancedout and'may be utilized.

2. Means for selectively receiving radio signals comprising an aperiodic antenna, an amplifying stage comprising a thermionic valve having an input circuit arranged to be energized from said antenna'and an output circuit comprising a tunable loop-antenna, means for coupling said output circuit to signal-indicating means, and means whereby potentials appearing across said output circuit by reason of signals received on said aperiodic antenna may be balanced against potentials developed in said output circuit by reason. of the direct reception of signals on said loop.

3. A receiving circuit for wireless telegraphy and telephony which comprises a triode valve, an open earthed aerial in series with a high resistance, the two ends of which resistance are connected, respectively, to the grid and to the cathode of said three-electrode valve, a loop aerial and an adjustable condenser connected across its terminals, the

' one or the other plate of said condenser being adapted to be connected to the anode of the valve by means of a two-way switch, and a high-tension battery, the positive pole of which is connected to the electrically symmetrical mid-point of the. loop aerial.

4. A directional receiving circuit for wireless telegraphy and telephony comprising an aperiodic open aerial, a tunable loop aerial and means for equalizing the electromotive forces derived from the open aerial, due to a given signal, with the corresponding electromotive forces in the loop aerial circuit, and means for applying said equalized openaerial elcctromotive forces to the loop-aerial circuit so as to oppose and balance out the aforesaid loop-aerial electromotive forces, whereby the respective electromotive forces due to another signal of different direction or wave length, or both, are not balanced out and can be utilized, and in which the loop aerial forms part of the tuned anode circuit of a three-electrode valve, to the grid circuit of which the open aerial is connected, and in which the respective electromotive forces in the loop-aerial circuit are equalized by varying the amplification factor of the valve.

5. Means for selectively receiving radio signals comprising an aperiodic antenna, an amplifying stage comprising a thermionic valve having an input circuit arranged to be energized from said antenna and an output circuit comprising a tunable loop-antenna, means for coupling said output circuit to signal-indicating means, and means whereby potentials appearing across said output circuit by reason of signals received on said aperiodic antenna may be balanced against potentials developed in said output circuitby reason of the direct reception of signals on said loop, said balancing means including a resistor connected across certain of the terminals of said valve and a connection thereto from said aperiodic antenna.

In testimony whereof, I have hereunto subscribed my name this 9th day of May 1924.

NORMAN PULLEN HINTON.- 

